Ventilation system for motionpicture projectors



L. H. MOOMAW May 4, 1948.

VENTILATION SYSTEM FOR MOTION PICTURE PROJECTORS 2 Sheets-Sheet 1 FiledOct. 17, 1946 N RM 0 mm V W H L. H. MOOMAW 2,440,966

VENTILATION SYSTEM FOR MOTION PICTURE PROJECTORS May 4, 1948.

2 Sheets-Sheet 2 Filed Oct. 17, 1946 INVENTOR LEW/S H. MOOMAW miniPatented May 4, 1948 VENTILATION SYSTEM FOR. MOTION- PICTURE PROJECTORSLewis H. Moomaw, Great Neck, N. Y., assignor to De Jur-AmscoCorporation, Long Island City, N. Y., a corporation of New YorkApplication October 17, 1946, Serial No. 703,805

1 9 Claims.

The present invention relates to a motion picture projector andparticularly to a ventilation system therefor. Y

The degree and clarity of enlargement coincident with projection ofmotion picture film images are dependent upon many factors, one of whichis the amount of light available in the projector. Bulbs of sufiicientillumination power may always be used, but incandescent bulbs, when theyproduce light, also produce heat. Bulbs of wattage suflicient forefficient and adequate projection produce so much heat that a coolingsystem is necessary. The importance of this factor in projectors of thetype used in motion picture houses is very great since the lamps usedare of exceedingly large size. However, the solution is not critical,since the projectors may be made large enough and the cooling systemstherefor may be made suitable for sufficiently heavy duty without makingthe projector of a size prohibitive for such use. In the case of motionpicture projectors for home use, however, and particularly in the caseof such projectors adapted to receive small film, for example 3millimeter, the solution of the problem is much more difficult, sincesize, power consumption, and noisiness of operation are all criticalfactors.

While the heat produced in a projector by the light source affects allof the working parts, and particularly the moving parts thereof, itsmajor deleterious effect is exerted on the motion picture film itself.By the Very nature of the projection, each picture on the film must beexposed to a substantial part of the full force of the light from thebulb while it is stationa y with respect thereto for a short period oftime. Since the film is essentially delicate, excessive exposure to heatwill cause it to deteriorate, scorch, and even, in the case ofnon-chemically treated film, burst into flames.

Consequently, the factor which in the past has largely limited theillumination power of the bulb employed in home motion projectors hasbeen the inability of the film to withstand the heat generated by thelamp.

It is standard practice to employ a forceddraft cooling system in amotion picture projector whereby relatively cool air is drawn from theatmosphere, passed over the light bulb, cooling the same, and thencereturned to the atmosphere. While such a simple system ameliorates tosome extent the problems above described, it does so only to a limiteddegree. More complicated and efilcient systems must be devised.

It is, consequently, a prime object of the present invention to providea novel ventilation system for a motion picture projector which systemis so eificient as to permit the use of light bulbs of higher wattage,and consequent greater illuminative power, than has been possibleheretofore.

It is another object of the present invention to provide such aventilation system which simultaneously and efficiently cools both thelight bulb and the driving means for the projector and ventilationsystem.

It is yet another object of the present invention to devise aventilation system which provides a maximum cooling effect at thoseparts of the projector most vulnerable to heat, to wit, the parts wherethe film is exposed to the full force of the lamp.

It is yet another object of the present invention to provide such acooling system which performs the additional functions of improving theclarity of reproduction by keeping the path of light from the bulb tothe film free of foreign matter and also causing the film to lie flatagainst its guiding means to improve the evenness of focusing of theresultant image.

To the accomplishment of the foregoing objects and such other objects asmay hereinafter appear, my present invention relates to the ventilationsystem for a motion picture projector as sought to be defined in theappended claims and as described in the following specification, and inthe drawings attached hereto, in which:

Fig. 1 is a front perspective view of a projector, with the fan and thelight bulb shown in phantom;

Fig. 2 is a rear perspective view of the same projector;

Fig. 3 is a side view of the fan employed;

Fig. 4 is an end view thereof;

Fig. 5 is a perspective view similar to Fig. 2 with certain of theprojector housing parts in exploded position;

Fig. 6 is a detail perspective view of the aperture plate and hingedaperture gate of the projector; and

Fig. 7 is a schematic flow diagram of the ventilation system of thepresent invention.

The primary source of heat in a motion picture projector is the lightsource, usually an electric lamp 2 mounted in a lamp housing A. Thesecondary source of heat in a projector is the motor B which providesthe motive power for the projector.

The motion picture film C, that part of the projector most susceptibleto heat, is exposed to ae i ee the strongest heat effects during thetime that it passes over an aperture plate D containing a light apertureE through which light passes from the light bulb 2 to the film C. Theaperture plate D is so positioned in the projector as to be exposedsubstantially continuously to the light from the light bulb 2 and sinceit absorbs much for the light from the lamp 2 other than that whichpasses through the aperture E, the aper'-" ture plate D tends to becomequite warm and; tends to transfer its heat to the film '6. Hence coolingof the aperture .plate D is of great importance.

In addition, it is of extreme impeit'iiii'ee thati the aperture be keptfree of foreign matter, since any such foreign matter woulddirctly.rater:

fere with and cut off the light used for projection purposes and wouldbeprojected in greatly mag: nified size onto the screen. It will also beapparent that it is essential for clarity of focusing that the Clioabsolutely flat against the apertures. V g y v A It is, t remrei eeessawthatfa'n eiriti ht"vehtilatiofl's'ystern coolthe rrfotor Band the lamp2, themin'or and major heatsources respectively. It is also exceedinglydesirable that the aperture plateD hemmed; The amou'r'itof coolingnecessary "for the iridtor Band the "aperture plate D is considerablyless than that necessary; in I the lamp housing A to cool the lamp 2.Consequently, lesser amounts of air are eeaea ier the first twofunctions than'for the last."

In order to achieve un'ifor'm eoo hhg'c the ehthe projector; .thejvehti-Iat qn system "of my invention (shownschem ally in FigJ 'Y) compr'ises fan F 'w'it'hair *ihletG aimsi outlet H in conjunction withmeans to guide on'e body of coolant Ta'ir wire 4') over the-'hcitbrBahdto the fan inlet (3, iiieaiistcgiiiaei another body ofcoolant airiarrow f6) "from he "a mosphere past the "aperture plate D toffan nlet 1G; and means to guide air 'froi'r' fthe"fan" emet- H to thelamp housing A in'forder 'toco'ol the lamp (arrow 12).

Since, as hasheen stated, mdre coolant "air is requiredfo "the p nanfbrth'e motor B'or the aperture plate Dgat rd bodydf a rfarr'ow 8)takeii'direfctly frofnjth atmosphere may be guided to, the ran antGlnad'dition to the bodies of air fr'epre'sentedfby;arrows t he f6;

As esi ir i er ut very important modification, the Tani) sq constructedas'to have two air inl'tsfG, G 'aially fd se'd' withrspect to saidia me'a'irinl G ein'stada ited-te er fresh cool mixer-raw rt) into the fanand he air inlet G being adapted todraw into thefan the" bodies of air 4and" Fwhich have previously cooledthe motor}; and the aperturefp'late D,respectively, and also; optionally, the air 8; The air thus drawndin e"'fan"throiigh inlets G, 'G' is-critrifugallyiorcd out 11' efr'o'ininadirection perpendicular to the EXl SliOf the ffafn as shown by arrow [2of Figs. 3 and 7,"and"i's then directed loy suitable "means "the laniphousing A; Afan'c'onstruoted'to performi'n thisfashion materiallyincreasesthe amount of fair and materially 'dec'r "es the temp'erature'of the air which is, "diree'tea't the iamii housing A; thus achievingmaximuinfcooling "or theflainp 2; the primarys'ource ofheatin heprojector. ln view tithe fact that "the bulk ;i th coolant air for theie'iii' 2 1eemes i i'reet1 "i rg the atmosphere to the rein F (arrays sand 1 B'Yarid s "directed from the fan directly to the la 7 housing-A(arr wfln 'that'iair 'i tsiib eete t H pf frictional fi cfswhl'ch wbumserve to raisedts 4 temperature, performs substantially no cooling otherthan cooling of the bulb, thus similarly keeping its temperature down,and places a somewhat smaller load on the motor B which must 5 drive thefan F, thus reducing the heat evolved in the course-of projection.

In order for the air to "cool the -aperture plate D the air need merelypass around it. However, 'in order to perform the additional functionsof lfl mainta ining'the aperture E free of foreign matterand'maintaining the film C pressed closely thereagainst, it is essentialthat the means which guides cola airy-past the aperture plate D tothe-fan inletfcelafdditionally guides said air past '15 the apertureE"6verthe inner surface of the aper- 'tur plate D; The air so guidedwill, as it passes oyer the orifice E, exert a suction elfect thereonwhich iii/"ill act to draw any foreign matter which may be in theorifice -E out therefrom and will also aet'te draw thefilhi "0' "flatagai'nstthe aper- -'ture-p-la teD as it passes ever the lih apertureHaving thus described the generic principles involved myhhveiyehtir iohsystem, -I shall rt'ablehome motion picture 'ci ples i i ayery A Thedrawings 7 g p ion-relate specific'ally to aprojector of a apted toreceive "8" millimeter film and herfce of comparatively small size, hiift l rinciplS ab'oye set-forth ma of T vie projectors of otheresteem-{meter housing-3o a. a electric meter B s sup orted, a fan housng 32 which is dispo'sed fa'nF, a lamp hbu'si gain which is sispeseaaamp 2, a'projection inaclxi nei 'y Housing sag-a a'r he heusiiig "33} apair' o'fre' 38 and ll! r tataibly aeiiiit daP'flwfe e"miities ei-reeiarm 42" and t4 conventional s'preehe 'wheei assemblies 46 has 48 mlgtiiding th'e filr ni"aperture plate n for 'res thcting the light fro'inthe bulb to an area equivalent to one *f-ialil of the inotion -pictureand a' g-a-t' 511}! edly ai'ttaohed ther'eto by pi'a-no h Tg'e52 =a' "d'carrying a lens assembly 54 2nd spi-ihg ioauee-pressureplate 56 formaintaining-- the filfn' C in -'cOi1taCt-iwith' the tip erture plate Dfor properlyidirecting-and focusing-the prcj-ected 'iriiagi All ofthehbbve' elelnen ts may "16%, iiept i ai's fireinaftr 'specifically'described, of bohyritiona'l "construction insofar as this invritiiin isconcerned.

The ventilation systempf myzinventionresides in the particular'arrangements' and adaptations hi the above m'entioned part's toachi'eve'the ad- 'va-ntageous rsultsdescribd abover- Ina'chieving thoser'sults;the=ian *F; Of the'geIierail-type illustrated in detail in Figs.3 and 4, may be employ'ed. This fan F comprise a pair of spacedsubstantially annular end plates 58 and 60 between which and fastened towhich are a plurality of fanbla'des 62 substantially radially disposedso that when said fan F is rotated about its axis, air in the interiorthereof is centrifugally forced out therefrom in a substantial radialdirection, as indicated by the arrows l2. The lack of air in the centralportion of the fan F created by this action permits atmospheric pressureto shaft 64 and the fan F are suitably connected,

as by keying, so that the motor B may drive the fan F in rotation.

It is thus apparent that as here illustrated the motor B is mounted inits housing 30 in axial alignment with the fan F, but it should beunderstood that other arrangements are possible so long as an air pathis provided over the motor B to the fan F. At the end of the motorhousing 30 opposite from the fan F are a plurality of air inlet passages66. When the switch [8 is thrown to the start position, the motor B willrotate causing the fan F to rotate, thus forcing air radially out fromits interior. The fan F therefore sucks air in from its axial directionsG, G, and some of the air which acts to fill the vacuum created by thefan action enters the housing 26 through the air inlet passages 86(arrow 4) passes through the motor housing 30 and over the motor Bcooling the same, and then enters the fan F via fan inlet G.

In the housing 26 directly adjacent to fan inlet G there may be a seriesof air inlet orifices 68,

through which room air enters (arrow 8) directly, mingling with the airrepresented by arrow 4 and passing into the fan F. Since this air entersthe fan F without passing through lengthy and restricted, and hencefrictional, passages, it enters in large quantities, at low temperature,and without placing excessive load on the fan F.

At the end of the fan housing 32 opposite from the motor B are anotherseries of air inlet openings 10. As the fan rotates, the air whichenters the fan via fan inlet G comes via these openings 70 (see arrowsl) and mingles in the fan F with the air which has entered via fan inletG. The comments in the preceding paragraph relative to the air of arrow8 apply equally to the air of arrows ID.

The housing 26 between the fan housing 32 and the lamp housing A definesone or more air passages such that the air forced out from the fan F(arrow [2) is directed to the base of the lamp 2. Heat-resistant plates12 and M in the lamp housing A (see Fig. then guide air up over the bulb2, cooling the same, and out through air outlet orifices 16 in the top18 of the lamp housing A.

By the structure as thus far described, it will be apparent that byconnecting the motor B to the fan F so that an air path is provided overthe motor B and to the fan F, by providing air inlet orifices 66 and/or68 and/or in the housing 26, the former in the end of the motor housing30 opposite to the fan F and the latter directly adjacent to the fan Fand by providing an air passage from the fan F to the lamp housing A, avery eiiicient ventilating system results whereby the drive motor may becooled and the air coolant 4 therefor, before being employed to cool thelamp 2, the major source of heat in the projector, is first mixed withfresh cool air entering through air inlet openings 68 and/or 10 thusreducing its temperature and augmenting the quantity of air coolantavailable for cooling the lamp 2.

During projection, the film C (see Fig. 6), provided with sprocket holesis adapted to move over the aperture plate D and past the light apertureE therein, said motion being actuated by movable claws 82 engaging withthe sprocket holes 80 in conventional manner. The light from the lamp 2passes through condensing lens 84 mounted on baffle plate 88, throughthe light aperture E in the light aperture plate D (the inside of whichis obscured in Fig. 5 by a fire shutter 88 which during movingprojection will move up to clear the aperture E in conventional manner)and through the film C, the registering aperture 90 in the pressureplate 56, and the lens assembly 54 to the projection screen.

It will, as has been above explained, be seen to be exceedinglydesirable for a ventilation system to effect direct cooling of theaperture plate D, thus protecting the film, that part of the projectorassembly most susceptible to heat, at the point where it is exposed tothe greatest heat, and simultaneously effecting a cleansing of theaperture E.

This may be accomplished by providing a plurality of air inlet orifices92 in the aperture plate D adjacent to the aperture E and on the sidethereof opposite from the fan F. The baffle plate 88 prevents air whichenters the housing via the air inlet orifices 92 (arrow 6) from goingdirectly to the lamp 2. The air is instead deflected (see the dottedlines of Fig. 5) and caused to pass over the inner side of the apertureplate D and the aperture E, then over the projection machinery,generally designated as 94, and then to the fan F into which it is drawnthrough fan inlet G along with air (arrow 4) that has entered throughair inlet orifices 66 and which has passed over the motor, andoptionally along the air (arrow 8) that has entered the housing 26through air inlet orifices 68.

The air represented by arrow 6 performs a number of functions:

1. Its primary function is to directly cool the aperture E, thus keepingthe temperature of the film C at a minimum.

In passing over the inner side or the aperture E, it tends to draw outof the aperture E any foreign matter which might have been lodgedtherein, thus ensuring a clean aperture.

3. By virtue of the same suction which keeps the aperture E clean, thefilm C is drawn tightly thereagainst, thus ensuring clarity of focusing.

4. The air also passes over the projection machinery 94 cooling thesame.

By employing the ventilation system of my invention in the projector asabove described, I have found it possible to employ light bulbs of 750watts and even 1,000 watts in a small 8 millimeter home motion pictureprojector, whereas the employment of conventional ventilation systems ina projector of that type would not permit the use of lamps of thatpower. Since the main disadvantage of 8 millimeter film is its smallsize, and since the amount of magnification in projection is determinedin part by the intensity of the light source available, my ventilationsystem by permitting the use of a light bulb of increased intensity,permits greater eniargem'ent andzthusconsiderahlyiri reaeeslth ldsirability .oi projectors :for small size film. It willzbe apparentthatmany chan es may h made in the specific design of a yentilationsystemfora-moviei roiector withoutdeparting from the spirit ofthe invention asdefined ;:in theafollowing claims.

.I claim: v

I emotio p r lm n eiee er eemnr ing a lamp housi a an h vin a ai inle nan air o t et, a me e :fo sa d p eieei r and ,a :light aperture platehaving an aperture past which the film is adapt d to s id a ventilatedsystemcomprising means-to uidelcoolant air. through said motor tosaid:fan inlet, mean to guide coolant .air pastrsaid aperture :to said .faninlet only vover the inner surface of said r-apertureplate soastosuckthe fihnclosethereto, andlmeans to guide air from said tanoutlet to said lamphousing, whereby said motor and aperture plate arecooled and said lamp housing is cooled by the coolant from said motor:and said aperture plate mixed with air from-the :atmos phere.

2. In a motion picture film projector comprising alamp housing, a ranhaving'an air inlet and an air outlet, a motor for said projector,

and a light aperture plate having an aperture past which the film isadapted to slide, a ventilation system comprising means to guide coolantair through said motor to said ian inlet, means to guide coolant airpast said aperture only-over the inner surfaceof said apertureplate tosaid fan inletso-as to suck saidfilm close to said apertureisaid inletadditionally-communicating with the atmosphere, and means to'guide airfrom said fan outlet to said lamp housing,

whereby said motorand-aperture plate are cooled and said lamp housing iscooled :by thecoolant from said motor andsaid aperture plate mixed withair from the atmosphere. 1

3. In emotion picture film :projectorcomprising .a .lamp housing, a fanhaving an air inlet and an air outlet, and -a light aperture plateoverwhich the film is adaptedto slide and .hav- .ingia light aperture, aventilation system-comprising means to guide coolant air past said lightaperture only over the inner surface of said aperture plate to said faniinlet so "as to suckesaidfilm close thereto,'andmeans to guide air fromsaid efanoutlet to said lamp housing, whereby said apertureplateseandlsaidilamp housing are .cooled.

:4. aInzamotion picturerfilm projector comprise inga damp housing, a:fan having .two .air inlets axially .disposed with respect theretoeandian ,air

outlet, a motor for said projector, and a light aperture plate having alight .aperture, a yentilation system comprising means to guide 7000,1-

ant air through said motor to one of :saidianinlets, means to guidecoolant :air-ipastisaidlight aperture only over the inner surface ,ofsaid 7 aperture plate to the same fan inlet, said other fan inletcommunicating directly with the-atatilation system comprising ;aprojector housing,

motor-d iven i amennte t ere n azl ehtaaeitu e plate er es .h eli elileme t d the ein an en iainrae ape tu e tli e w ei ht nasseerfe nr ie tp.:n rine es, ad 3 nr in a h us n t perm t a to. ente e .n. teet r eniheeisie e 3. 1Q ae r i re erree. ernsaiiian and to al e ais t .eeressaid aeett e 9 313" t e inside e said aperture pla e whereby the ne ainea sa d l ght-ape t reeeelesaid a er ure Plat k ns ai ape tu e re e ieeiee ma ter, and t e dim efi ther aaainet V In a moti n p etu e prqi tera venti etien ea ern m ie n P eieete heee a em tteraten an mQii-n eeihen, ighth-ta e tare p a mounted in ea-i re ee e hei e n an eee e nieg ana e tur thr a en whieh li h na eee -er rreie ti n ,P tee es en e s ontaiin a nta rifi l ca d: adiaeent t sai aperture and on the opposite $521?iiherepf from sa d said musin r v d ng ventilat eng ease t g de air whch e ters e id 1 Qiee t e iah sa d an i take o ifi es eeres s i ap rtenl 0n the inside e e id, a e tu plat w ierelq he .fla stai es eei li hta u 9015 sai a er ur ma e .ke a d a e u vt ee ie e e 'an matte ma n a nst m a er ee ns :I a modem pic ure fil nrqi e or a ventilat on s s e ee ifis ne a rqie ter ho s ng, a l m hous -.m un ed here n. a e er a a ianriren her b meu te i ea d eieete hou ing, ai in e -r pen ng i said preiee hellsne e t e side o the mete enees te om sa ien-a r in e evenings isaid eroie te h us n on th a d (el a d t n opp si e i iem t me er a li hap rture p a m u ed in sa p elat housing and containing an aperture fromwhich light pas e ie pro ect n p r s s and r the .fiim i ada ted t s deand also conta n n a nta e ie ifi e eate ad a ent t sai ane eend enlytetheqpP e t si e-th en eaid p eieet housin providne Raine to -gu de eneIbe y a e e said ,n eiee er eusing th ough the tthie i en.

enen nee en -eiee e t e m t ee e to said fen, i aid me e ee i t a e a da ..QtheI .eheei 1 a r, which nte s sa d pr je lia e ne tb enah the erfiees diae nt ethean a ros sai lieh ape u e only on he inside .e aidaper u e p ate wh b ai a e u plate is cooled, and a third body of air,which en rs threuen the en n nas en the side of th fiane neei e to saideter to m x -tl t e e two'bodies-of betore the resultant air mixturepasses tothe lamp housing for cooling purposes.

8211A- re t le en s st m f r a modem picture i ie ter ee n is n e nreieter hei s ne, a

hi ie i n i e. e ei r n aid hensinao ,ne e e said hem ateen a a e in sada aiiie n etetax ieht a ertu e pa t i s qh n uineen hee her s de oiee enamep a e sa d .aeertlin w late eentaining an ap rtur th whi h li ht p ses zior p o e tion nureese an past which the film is adapted to slideand also eqnteinine a r intak @e t iiees-leeated a en ea s eeee nre andth ep Q -te s d he e i n; sa d len ai h in the eb p ovidin a ent iatienha h wh r b ai ma en er ai housin t rei h said e ifi es th a eitileendthenn s aere eai -an ar Even y .o

-.in icie ofsai p a e and th enehlaa d l afl re at intosaid: an, c.Qo is-ea die ertiir :lseepins e ciiereiemmat e a d aintainin the.metien:n en ei-filmfletwthere eainet.

9. A ventilation system for a motion picture film projector comprising aprojector housing, a baflle plate mounted therein, a fan in said housingon one side of said baflle plate, a driving motor for said fan on theother side thereof, an air passage in said bafile plate between said fanand said motor, a light aperture plate in said'housing on the motor sideof said battle plate and containing an aperture through whichlightpasses for projection purposes and past which the film is adapted toslide and also containing air intake orifices located adjacent to saidaperture and on the opposite side thereof from said motor, air inletopenings in said housing on the side of the motor opposite from saidfan, air inlet openings in said housing on the side of the fan oppositefrom the motor, a lamp housing in said projector housing on the fan sideof said baftie plate, said projector housing providing an air pathbetween said fan and said lamp housing whereby a body of air may entersaid projector housing and pass over said motor cooling the same,another body of air may enter said projector housing through theorifices in said aperture plate and then, deflected by the baille plate,pass across said aperture only on the inside 01' said late, and both ofthe above mentioned 10 bodies of air may be mixed with a third body ofair which may enter said projector housing via the air inlet openings insaid housing on the side of said fan opposite from the motor, theresultant air mixture then passing to the lamp housing.

LEWIS H. MOOMZAW.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,587,955 Howell June 8, 19261,891,683 Morsbach Dec. 20, 1932 1,921,214 Carpenter Aug. 8, 19331,944,029 Foster Jan. 16, 1934 2,135,500 Floster Nov. 8, 1938 2,186,618Philips Jan. 9, 1940 2,194,585 Brenkert Sept. 2, 1920 FOREIGN PATENTSNumber Country Date 379,175 Great Britain Aug. 25, 1932 510,255 FranceSept. 2, 1920

